Independent testing performed by the AP has revealed that Comcast actively interferes
with peer-to-peer traffic going to and from its high-speed internet subscribers, by impersonating
users’ machines and sending fake disconnect signals.

While traffic shaping – the act of throttling a given piece
of Internet traffic based on its type, like BitTorrent or VOIP – is becoming
increasingly common amongst ISPs interested in preserving quality of service, it
seems that Comcast is one of the first companies that actively impersonate individual
connections. Most providers will simply slow down some traffic in favor of
others, or block a protocol’s port number to prevent it from functioning.

According to the report, Comcast’s technology affects users
across many different networks, including e-Donkey, Gnutella, and BitTorrent. Robb
Topolski, a former software quality engineer at Intel and Comcast subscriber,
began to notice unexplainable performance problems with his P2P software.
Posting to the popular forum DSLreports.com, he collected similar reports from
other Comcast users around the country.

In the case of BitTorrent, Comcast’s technology only kicks
in when a user’s client has a complete copy of the file and is uploading it to
other users, and not while downloading.

Comcast spokesman Charlie Douglas would not comment directly
on the matter, instead only saying, “Comcast does not block access to any
applications, including BitTorrent.”

There are currently very few regulations regarding traffic
shaping, and none that specifically cover Comcast’s particular use. The FCC
says that while consumers are entitled to run the applications and services of
their choice, they are subject to measures of “reasonable network management” by
their ISPs. The closest directive governing Comcast’s behavior – which still doesn’t
directly apply – would be found in AT&T’s conditions for acquiring BellSouth,
where it had to agree not to manipulate traffic in any way based on its origin –
not service type.

Comcast’s “traffic discrimination” has important
ramifications for the growing number of services that are leveraging P2P as a
means to distribute large files quickly and cheaply. A company like Blizzard
Entertainment, who relies on BitTorrent for distributing World of Warcraft updates that often measure hundreds of megabytes
in size, may have trouble reaching its players if it or they are behind a
Comcast internet connection. This problem will only worsen if other ISPs decide
on a similar course of action.

Ashwin Navin, co-founder and president of BitTorrent Inc.
confirmed the AP’s findings, and noted that he has seen similar practices from
several Canadian ISPs.

“They're using sophisticated technology to degrade service,
which probably costs them a lot of money. It would be better to see them use
that money to improve service,” said Navin.